Every ten years I believe. Plenty of time to prep for the next one.
It varies, depending on things like number and type of polyps found, family history of colorectal cancer, etc. I've had intervals of as little as one year recommended, though I have to admit I went a good bit longer. The most recent one was just a couple of weeks ago and they said five years, so that's good.
Next time I will just eat a Burger King breakfast. It does the same thing.